Oral tolerance is classic method by which one can induced immunologic tolerance and it is now recognized to be an active immunologic process mediated by multiple mechanisms including active suppression, anergy, and deletion. Low doses of oral antigen administration favor induction of regulatory T cells whereas higher doses induce anergy or deletion. Over the past decade there has been increasing interest in oral (and mucosal) tolerance with the demonstration that orally administered antigen can suppress several animal models of autoimmune disease includingEAE. Furthermore mucosal antigen administration may have even broader biologic implications as a therapeutic modality for neurologic diseases including Alzheimer's disease and stroke. Human trials of oral tolerance have given mixed results and a great deal remains to be learned about the basic mechanisms that underlie immune responses in the gut associated lymphoid tissues (GALT) and both the inductive and effector mechanisms associated with oral tolerance. We will continue our investigation of oral tolerance as one of the projects in the program project grant and will address the following questions: 1. What is the role of T-bet transcription factor in the induction of mucosal tolerance? T-bet is a major regulator of Thl differentiation and we have found that T bet -/- animals have a phenotype analogous to that observed in low dose oral tolerance. We will investigate the role of T-bet in the induction of the different mechanisms of oral tolerance. 2. What is the role of T-bet and TIM molecules in TGF-0 producing Th3 type regulatory cells? We have shown that the gut is a unique environment that leads to the induction of TGF-p (Th3 type) secreting regulatory cells and cells which express LAP on their surface. We will investigate T-bet and TIM molecules in Th3 clones derived from the mesenteric lymph nodes of low dose orally tolerized animals. In addition, we have generated a TGF-P transgenic mouse in which the production of TGF-|3 is inducible in T cells, driven by the IL-2 promoter. These mice will be used to investigate the effector function of TGF-P secreting regulatory cells. 3. What are the mechanisms associated with enhancement of oral tolerance to glatiramer acetate and MOG by novel mucosal adjuvants that polarize towards Thl vs. Th2 responses . Mucosally active adjuvants may be crucial for the induction of immune responses of significant strength to be effective as immune therapy. We will investigate unique adjuvants that polarize towards Thl/Th2-Th3 responses when given orally in the investigation of glatiramer acetate, a immunomodulatory drug currently approved for the treatment of MS, and MOG an encephalitogenic myelin antigen.